The invention relates to a method for the combined determining of a momentary roll angle of a motor vehicle and a momentary roadway cross slope of a curved roadway section travelled by the motor vehicle as well as a device for the combined determining of this momentary roll angle and this momentary roadway cross slope. The invention furthermore relates to a motor vehicle having such a device.
Electro-hydraulically active chassis systems are known by the term “Active Body Control (ABC)”, which, besides a conventional spring and dampener function, also allow the possibility of the targeted setting of pitch and roll angles. A roll is therein referred to as a rotational movement of a motor vehicle around its longitudinal axis. Such a roll movement can result during travelling of a curved roadway section by the motor vehicle if the motor vehicle inclines outwards around a determined roll angle due to the occurring centrifugal forces. The roll angle set here depends on the transverse acceleration of the motor vehicle, the center of gravity height, the chassis construction of the motor vehicle as well as the speed thereof.
The centrifugal forces occurring during travelling of the curved roadway section are often uncomfortable to experience for the passengers of the motor vehicle and can therefore lead to a considerable reduction of the driving comfort. A possibility to reduce the comfort-reducing effect of such undesired transverse forces on the passenger of the motor vehicle consists in implementing incline technology in the motor vehicle by means of “Active Body Control (ABC)”, as has already been used for a long time in rail vehicles. By using such incline technology, it is possible for the motor or rail vehicle not to incline outwards during travelling of a curved roadway or rail section, but rather in the opposite direction, so inwards, due to corresponding control of a chassis of the motor vehicle. For this purpose, the chassis can be provided with suitable actuators, for example in the manner of height-adjustable struts which connect the vehicle frame to each wheel of the motor vehicle in a height-adjustable manner, such that a determined roll angle of the motor vehicle can be set.
As the centrifugal forces occurring during travelling of the curved roadway section depend on different factors, such as for example a roadway curvature of the roadway section or the momentary speed, the roll angle to be set in the sense of an incline technology on the chassis of the motor vehicle must also be determined depending on these parameters in order to ensure as high a level of driving comfort as possible for the passengers. In order to achieve maximum driving comfort, it can be required to also consider a momentary roadway cross slope of the curved roadway section being travelled by the motor vehicle during the setting of a determined roll angle in the motor vehicle. This is because, often, the roadway travelled by the motor vehicle is not aligned horizontally in its transverse direction with regard to a direction vector of the center of gravity serving as a reference, which defines a horizontal plane of the earth's surface, but rather is inclined relative to this “horizontal reference plane”. In particular, a curved roadway section can be inclined outwards with regard to the curvature of its curve, for example in order to facilitate a draining of rainwater accumulating on the vehicle surface, among other things. On the other hand, the roadway can also incline inwards in the manner of a so-called curve superelevation in the curve direction in order to facilitate the travelling of the curved roadway section for the motor vehicle. This means, however, that, in any case, the roadway cross slope of the roadway relative to the horizontal reference plane must be considered when controlling a chassis of the motor vehicle for the setting of an optimum roll angle of the motor vehicle.
DE 10 2010 046 317 A1 describes a method to set the spatial position of a roll axis around which the motor vehicle is able to rotate at a predetermined roll angle. According to the method, firstly in a first step, a spatial target position of the position of the roll axis is set and subsequently in a second step, a transverse acceleration of the motor vehicle is determined. In a third step, a target cross slope of the motor vehicle and target transverse offset of the motor vehicle is finally determined depending on the transverse acceleration such that when setting the target cross slope and the target transverse offset, a transfer of the roll axis into the target position is caused. In order to ensure that the motor vehicle occupies the target cross slope determined in the previous step, at least one actuator of an active chassis device of the motor vehicle is adjusted accordingly. Additionally, at least one actuator to influence the transverse movement of the motor vehicle is adjusted in such a way that the motor vehicle additionally also occupies the target transverse offset determined in the previous step. The expected transverse acceleration can, for example, be determined with the aid of a camera system attached to the motor vehicle, which optically detects the curved roadway section in front of the motor vehicle which is to be travelled and analyzes it to determine the expected transverse acceleration.
DE 10 2006 018 978 A1 describes a method for determining a roll angle of a motor vehicle having at least one device for determining the yaw rate or a value correlated thereto as well as a device for determining the vehicle speed and, if necessary, a camera system which is directed forwards. The roll angle is determined by using the yaw rate or a value correlated thereto and the specific roll spring stiffness of the vehicle.
An object of the present invention is to specify an improved embodiment for a method for the combined determining of a momentary roll angle of a motor vehicle and a momentary roadway cross slope of a curved roadway section travelled by the motor vehicle. It is likewise an object of the present invention to specify a device for determining such a momentary roadway cross slope.
The invention is based on the general idea of determining both the overall momentary vehicle roll angle of the motor vehicle relative to a horizontal reference plane and a momentary roadway cross slope of the curved roadway section travelled by the motor vehicle relative to the horizontal reference plane from the chassis data and the transverse dynamics data of the motor vehicle travelling the roadway section, during travelling of a curved roadway section. Thus, as has already been explained, a plane running in parallel to a direction vector of the gravitational acceleration is meant by horizontal reference plane; the roadway section travelled by the motor vehicle in the transverse direction can be inclined relative to this reference plane.
The method according to the invention can be implemented in a simple manner in a motor vehicle, as chassis data and also transverse dynamics data for a great variety of purposes can be determined as standard by means of the sensor system integrated into the motor vehicle and, for example, can be transmitted to a control device integrated into the motor vehicle, wherein the control device controls different vehicle components, in particular the chassis, of the motor vehicle based on this data.
The method according to the invention can be implemented in real time in a motor vehicle, in particular in a control device (ECU) integrated into the motor vehicle, such that this data can be considered, if necessary, during the control of the chassis of the motor vehicle or further vehicle components based on the roadway cross slope or the momentary vehicle roll angle determined by means of the method according to the invention.
In a preferred embodiment, the chassis data comprises a momentary tire roll angle of the tires of the motor vehicle or/and a momentary chassis roll angle of the chassis of the motor vehicle. The momentary chassis roll angle can be determined by means of a suitable sensor which is integrated into the struts of the chassis. Alternatively to this, however, it can also be conceived that the determination of the chassis roll angle occurs without such a sensor system, for example if the struts of the chassis are controlled directly by means of the control device to set a determined vehicle roll angle. In this case, the set chassis roll angle can also be read directly from the control device which controls the struts of the chassis. The same applies for the tire roll angle of the tires of the motor vehicle which can depend, in particular, on a wheel load change between the left and the right tires of the motor vehicle as well as a tire pressure-dependent stiffness of the tires and therefore can be determined by means of suitable (tire pressure) sensors integrated into the tires of the motor vehicle. According to this embodiment, the transverse dynamics data comprises a momentary transverse acceleration of the motor vehicle. The momentary transverse acceleration of the motor vehicle can thus be determined by means of an acceleration sensor integrated into the motor vehicle.
In a particularly preferred embodiment, the method according to the invention can comprise two consecutive method steps S1 and S2. In the first method step S1, the momentary vehicle roll angle φA is calculated from the momentary transverse acceleration ay, the momentary speed vx and the momentary yaw speed d/dt ψ of the motor vehicle according to the equation φA=(1/g) (ay−vx d/dt ψ). In a second step S2, then the momentary roadway cross slope (φFB) is calculated from the momentary vehicle roll angle (φA), calculated in step S1, a momentary chassis roll angle (w) and a momentary tyre roll angle (φR) according to the equation φFB=φA−w−φR.
In a particularly preferred embodiment, it can be conceived that the determination of the momentary roadway cross slope occurs using GPS-based map material of the travelled curved roadway section, interacting with a GPS receiver for determining the momentary vehicle position of the motor vehicle. Since, even in modern map material, information with regard to local roadway cross slopes is not present or is only present with a low level of accuracy, such a use in the first instance can occur only in a supplementary way during the determination of the momentary roadway cross slope according to the invention.
The invention also relates to a device for the combined determining of a momentary vehicle roll angle of a motor vehicle and a momentary roadway cross slope of a curved roadway section travelled by the motor vehicle. The device according to the invention comprises a control device which is able to be connected for communication to a transverse acceleration sensor, a yaw rate sensor and a speed sensor of the motor vehicle for the transmission of a respectively measured momentary transverse acceleration or momentary speed to the control device. The control device determines the momentary vehicle roll angle of the motor vehicle and the momentary roadway cross slope of the curved roadway section travelled by the motor vehicle from chassis data and transverse dynamics data which comprise the momentary transverse acceleration or momentary speed of the motor vehicle by applying the method according to the invention.
The invention also relates to a motor vehicle having a device which is explained above, as well as having a transverse acceleration sensor, a yaw rate sensor and a speed sensor which are each connected for communication to the control device for the transmission of a measured momentary transverse acceleration, a momentary yaw speed or a momentary speed of the motor vehicle.
Further important features and advantages of the invention result from the sub-claims, from the drawings and from the relevant description of the figures, by means of the drawings.
It is to be understood that the features referred to above and still to be explained below are not only able to be used in the respectively specified combination, but also in other combinations or alone, without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are depicted in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.